Dwejra, Gozo · Advanced · 3-40m

Inland Sea
and the 80m tunnel

Name: Guided Dive
Brand: diveshack

The Inland Sea is a natural lagoon at Dwejra, cut off from the open Mediterranean by a cliff. An 80-metre tunnel bored through the rock connects the two: enter at 3m inside the lagoon and emerge at 26m into open water, where a vertical wall drops into the blue. The same headland as Blue Hole, but a completely different dive.

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Depth Profile

History & Background

Geological

The Inland Sea at Dwejra is a collapsed sea cave: a roughly circular lagoon of seawater connected to the Mediterranean by an 80-metre limestone tunnel. The lagoon sits at sea level and the tunnel descends to around 26m on the open-sea side. The formation was created by wave erosion and limestone collapse over thousands of years.
Ancient

Dwejra Bay has been settled and used by fishing communities since antiquity. The Inland Sea lagoon provided a sheltered harbour for small boats; wooden luzzu fishing boats still operate from it today. The tunnel mouth on the open-sea side was historically used by small fishing craft in calm conditions.
Today

The Inland Sea tunnel dive is one of Gozo's most iconic experiences. Divers enter from the sheltered lagoon, navigate the 80m tunnel, and emerge on the open-sea side at 26m. The dive can be done in either direction. The site is also popular with snorkellers inside the lagoon. Weather-dependent: the tunnel exit must be calm.

The dive begins inside the Inland Sea lagoon, an enclosed body of crystal-clear seawater. Small luzzu boats take divers to the tunnel mouth, which opens at approximately 3m depth. The tunnel descends gently from 3m at the lagoon entrance to 26m at the open Mediterranean exit. Light decreases progressively through the tunnel, but the exit glows with natural light on sunny days, creating a dramatic silhouette effect. The tunnel walls and ceiling are covered in cup corals, sponges, and nudibranch species. At the open-sea exit, the reef wall drops away to the depths of the Dwejra channel. Grouper and amberjack are regularly seen at the exit. Return through the tunnel or ascend the outer reef wall. Strong current can occasionally affect the outer exit; always check conditions before entry.

Points of Interest

Inland Sea: what to look for

Looking out through the Inland Sea tunnel toward open water, Dwejra Gozo

3m to 26m

The Tunnel

The tunnel runs 80 metres through the cliff face. It is wide enough that surfacing is possible at any point along its length. The gradient is steady: 3m at the lagoon entrance rises to 26m at the open-sea exit. Light from both ends illuminates the passage during midday dives.

The Inland Sea lagoon at Dwejra, Gozo, from the water surface

0-2m

The Lagoon

The Inland Sea is approximately 60 metres across and sheltered on all sides by cliff walls. Maximum depth inside the lagoon is 2m. Tourist boats operate here throughout the day, so divers must stay below the surface and maintain awareness of boat traffic before and after the dive.

Diver exiting the tunnel at the seaward end, Inland Sea Gozo

26m+

Open-Sea Wall

Emerging from the tunnel at 26m, the seabed opens onto a vertical wall that descends well beyond recreational limits. Large gastropods colonise the wall face. Groupers are resident around the tunnel exit and eagle rays are occasionally seen crossing the open sand below.

Light filtering through the Inland Sea tunnel from above, Dwejra

3-26m

Midday Light

When the sun is overhead, shafts of light enter through fissures in the tunnel roof and refract in the water column. Divers face toward the lagoon entrance on the return leg and swim directly into a circular frame of blue-green surface light. Timing the dive for midday produces the best visual conditions.

Location

Where to find it.

// Dive Site Map · Dwejra · Inland Sea Tunnel

Getting There

Dwejra Bay on Gozo's west coast. Small luzzu boats ferry divers from the lagoon shore to the tunnel mouth. Car park and cafe on site. The Inland Sea lagoon is a short walk from the car park.

Coordinates

36°03'N, 14°11'E · Dwejra, San Lawrenz, Gozo

Inland Sea and Tunnel Diving Gozo dive site card

Dive Conditions

When to dive the Inland Sea

Period	Water Temp	Visibility	Conditions
Jan-Mar	14-16°C	25-35m	Very clear water; cold dive, 7mm suit recommended
Apr-Jun	17-22°C	20-30m	Good conditions; calm seas at Dwejra typical
Jul-Sep	25-28°C	20-25m	Peak season; warm, occasional jellyfish blooms
Oct-Dec	18-23°C	25-35m	Excellent visibility; northwest swell can affect open-sea section

Summer visibility (Jul-Sep)

Winter/autumn visibility (Oct-Mar)

Currents

Inside the lagoon there is no measurable current. In the tunnel, a gentle flow may run toward the open sea on an outgoing cycle; surfacing is possible throughout so divers can wait out any increased flow. The open-sea section can have a directional current running along the wall.

Entry and Exit

Shore entry from the Inland Sea lagoon is rated easy. Steps and a concrete platform provide access. Entry and exit are both from the lagoon; the tunnel is dived as a circuit exiting back through the tunnel on the return. Stay below 1m depth to remain clear of tourist boats.

Equipment Notes

A torch improves the tunnel experience even at midday. An SMB is required for any open-water portion beyond the tunnel exit. The site is sheltered enough to dive when Dwejra is exposed, making it a useful alternative on windier days. A 5mm wetsuit covers summer; 7mm for winter.

Dive Briefing

Safety and planning

Certification Level Required

Advanced Open Water or equivalent certification is required. The tunnel exit at 26m and the open-sea wall section place this dive in the advanced category. Divers should have logged a minimum of 20 open-water dives before attempting this site.

Boat Awareness Required

Small motorised tourist boats operate continuously inside the lagoon. Divers must descend immediately on entry and remain below 1m depth while crossing the lagoon. Before surfacing on return, wait under the water and confirm the lagoon is clear of vessels above you.

Torch Mandatory Required

Each diver must carry a torch. While natural light enters the tunnel, it is insufficient for examining the walls or managing navigation in reduced conditions. A torch also acts as a signalling device to other divers in the tunnel.

SMB for Open Water Required

If the dive plan includes time on the open-sea wall beyond the tunnel exit, deploy a surface marker buoy before ascending. Boat traffic operates in the waters outside Dwejra. Ascending without a visible SMB is not acceptable practice at this site.

Depth Limit Beyond Tunnel Required

The wall outside the tunnel drops beyond recreational limits. Agree a maximum depth before entry and treat it as a hard limit. There is no dive-specific reason to descend past 30m at this site on a recreational profile.

Tunnel Navigation Recommended

The tunnel is wide and the route is straightforward, but first-time divers benefit from a guided entry. Visibility inside the tunnel can temporarily reduce if silt is disturbed. Maintain good buoyancy and keep clear of the tunnel floor throughout the passage.

Book This Dive

Dive the Inland Sea with diveshack

diveshack runs guided dives to the Inland Sea and Tunnel as part of Gozo day trips. The site pairs well with Blue Hole on the same headland for a full Dwejra day. All dives include a site briefing, guided tunnel transit, and surface cover. Equipment rental is available.

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Inland Seaand the 80m tunnel